Digital three-dimensional object manufacturing, also known as digital additive manufacturing, is a process of making a three-dimensional solid object of virtually any shape from a digital model. Three-dimensional object printing is an additive process in which successive layers of material are formed on a substrate in different shapes. The layers can be formed by ejecting binder material, directed energy deposition, extruding material, ejecting material, fusing powder beds, laminating sheets, or exposing liquid photopolymer material to a curing radiation. The substrate on which the layers are formed is supported either on a platform that can be moved three dimensionally by operation of actuators operatively connected to the platform, or the material deposition devices are operatively connected to one or more actuators for controlled movement of the deposition devices to produce the layers that form the object. Three-dimensional object printing is distinguishable from traditional object-forming techniques, which mostly rely on the removal of material from a work piece by a subtractive process, such as cutting or drilling.
Additive manufacturing of three-dimensional printed electronic devices typically includes the formation of electrically conductive paths that are encased within electrically insulating structure. An example of a material useful for forming electrically conductive paths in an additive manufacturing process is an aqueous or solvent-based metallic colloidal solution and an example of a material useful for forming electrically insulating structure is an ultraviolet (UV) curable polymer. One challenge associated with building these devices by ejecting these materials is managing the changes that occur in the materials during drying, curing, and sintering of the materials.
One change that occurs when the metal solution is dried is shown in FIG. 4. The layer 412 is formed with drops 404 of a UV polymer and drops 408 of a metallic colloidal solution. As shown in the upper illustration in FIG. 4, all of the drops 404 and 408 have the same volume when ejected. During drying, curing, or sintering of the layer 412, the volume of the drops 408 of the metallic colloidal solution are significantly reduced as the water or solvent is volatized. The drops 404 of the UV curable polymer or other electrically insulating material, however, maintains approximately the same volume the drops had when they were ejected. The different volumes in the two materials occurring after the drying and curing of the materials produce voids or dips in the layer. Consequently, subsequent layers formed on this uneven layer can have deformities in their structure. An additive manufacturing process that enables level layers to be formed with materials having dissimilar shrinkage or reduction rates during drying, curing, or sintering would be beneficial.